A new malware family is targeting web servers worldwide in an attempt to ensnare them into a crypto-mining botnet, security researchers have discovered.
Dubbed RubyMiner, the threat was discovered last week, when it started launching massive attacks on web servers in the United States, Germany, United Kingdom, Norway, and Sweden. Within a single day, the attackers behind this malware attempted to compromise nearly one third of networks globally, Check Point revealed last week.
The purpose of the attack, which is targeting both Windows and Linux servers, is to install a Monero miner by exploiting old vulnerabilities that have been published and patched in 2012 and 2013. The attackers weren’t looking for stealth compromise, but attempted to compromise a large number of vulnerable HTTP web servers as quickly as possible.
The infection campaign is targeting vulnerabilities in PHP, Microsoft IIS, and Ruby on Rails. Despite the large number of compromise attempts observed, only 700 servers worldwide have been successfully enslaved within the first 24 hours of attacks.
The attack on Ruby on Rails attempts to exploit CVE-2013-0156, a remote code execution vulnerability. A base64 encoded payload is delivered inside a POST request, expecting the Ruby interpreter on the server to execute it.
The payload is a bash script designed to add a cronjob that runs every hour and downloads a robots.txt file containing a shell script, designed to fetch and execute the crypto-miner, but not before checking whether it is already active on the host. Not only the mining process, but the entire download and execution operation runs every hour.
“This is possibly to allow the attacker to initiate an immediate kill switch for the miner bot. If the attacker would like to end the process on the infected machines, all that needs to be done is modify the robots.txt file on the compromised webserver to be inactive. Within a minute, all the machines re-downloading the file will be receiving files without the crypto miners,” Check Point notes.
The deployed malware – on all infected servers – is XMRig, a Monero miner that was used in September 2017 in an attack exploiting a vulnerability in Microsoft IIS 6.0, the webserver in Windows Server 2003 R2.
One of the domains used in the newly observed infection campaign is lochjol.com, which was previously used in an attack in 2013. That attack abused the Ruby on Rails vulnerability as well, and also had some features common with the current incident, but the researchers couldn’t determine further connections between the two, especially with their purpose seemingly different.